JPS58121073A - Toner density controlling device - Google Patents

Abstract

PURPOSE:To expose plural reference patterns, and to detect them by a single detector, by switch-controlling plural reference patterns on a moving member instead of movement of an exposure optical system. CONSTITUTION:A mask plate 6 which is like a band and has a rectangular transparent window in the center is provided on the surface of the end part of an original placing plate in the right end of a platen 4. On this window, a circular arc plate-like moving member 8 is stuck to the tip part of an indicating pointer 9a of a moving coil type indicating instrument 9. On this moving member 8, a reference pattern of five blocks is formed. On this reference pattern, white and black are provided, respectively. A reference pattern image is exposed on the drum, is detected by a detector, this reference pattern input signal is compared with a prescribed reference value, is processed, a toner replenishing signal is outputted, and a toner replenishing device is driven.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a toner density control device used in electrophotographic copying machines and their applied equipment, etc. 0 First, a general explanation of the toner density control device Q. From toner and carrier. A device that visualizes an electrostatic latent image using a two-component developer for dry development or a developer for wet development consisting of toner and a liquid dispersion medium; -rPhotocopying machine or electrostatic recording device, etc. During repeated development operations, the density of the resulting visible image changes over time because the developer deteriorates or the ratio of toner in the developer decreases. Therefore, conventionally, the image density of an image pattern for density detection, which is visualized on a photoreceptor as a pattern corresponding to a reference pattern for determining developing ability, is used as the developed density. A sensor detects the amount of toner adhering to the surface area on the photoreceptor and the image density IW, and compares these with a certain standard value, and when it is determined that it is below the standard value By taking measures such as appropriately replenishing toner, the density of the visualized image corresponding to the original image is maintained at a constant level. A configuration consisting of a series of members designed for the above purpose is called a toner concentration control device.

By the way, conventionally, in a toner density control device that examines the amount of toner adhering to a portion corresponding to the background on a photoconductor and the image density, a method is used to determine the developing ability, as shown in FIG. 1, for example. Two reference patterns, black and white, are arranged on the contact glass 1 outside the document placement area. However, as shown in the figure, if the reference patterns 2 and 3 are arranged in parallel in the scanning direction When forming an image on a photoreceptor, there is the complication that the exposure element system must be moved in the scanning direction X.

Moreover, unlike the above, when the reference patterns 2' and 3"e are arranged in a direction perpendicular to the scanning direction X as shown in FIG. 2, in order to detect the density of the developed image, Two detection units are required: a detection unit for detecting the density of the image pattern corresponding to the reference pattern 2′, and a detection unit for detecting the density of the image pattern corresponding to the reference pattern 3′;
Therefore, it is troublesome to have to correct the error between the rain detection parts and the surface potential of the photoreceptor on the two detection surfaces, otherwise there is a problem that the toner concentration control is affected.

Roughly speaking, even in the arrangement of the reference patterns shown in FIGS. There is also the problem that the reference pattern gradually changes color and lacks long-term reliability.

SUMMARY OF THE INVENTION An object of the present invention is to provide a toner concentration control device that can solve the above-mentioned problems in the prior art.

Hereinafter, the non-invention will be explained in detail.

The toner density control device according to the invention includes a movable member having a plurality of reference patterns, and a means for controlling the movement of the movable member, wherein a reference pattern selected from among the plurality of reference patterns in the movable member is exposed. It is characterized by having a switching means for positioning at a predetermined spatial position on the object plane of the optical system.

FIG. 3 shows an example in which the toner density control device according to the present invention is installed in a dry electrophotographic apparatus. In FIG. It is located outside the area and is provided in a part of the contact glass 1 or adjacent to the contact glass 1.

As shown in FIGS. 4, 5 & C, a strip-shaped ask plate 6 is adhered to the right end of the contact glass book and the edge surface outside the document placement area. It is a transparent plate and is white in color to reflect light on the surface in contact with the contact glass 1. Note that a window 7, which is a rectangular opening, is formed in the center of the mask plate 6. A plate-shaped movable member 8 that moves in a plane parallel to the contact glass 1 is located directly above the window 7.

The movable member 8 has a wide arc shape as shown in FIGS. 8 and 9, and the surface of the movable member 8 facing the mask plate 6 is partitioned into five sections, for example. Each section constitutes a reference pattern.

To explain each reference pattern, in the example of FIG. 9, the reference pattern Px7% white is formed in the rightmost section.The reference pattern P2 on the left side of this reference pattern P is also white.
The reference pattern P3 to the left of this reference pattern P2 is a repeating pattern of two black and white lines that are substantially parallel to the radial direction of the arc of the movable member 80, and the reference pattern P4 to the left of this reference pattern P3 is a solid black pattern. , reference patterns Ps&d on the left of the reference pattern P4 are formed in white, respectively.

The movable member 8 is fixed, for example, to the tip of an indicator needle 9a of a moving coil type indicator indicated by the reference numeral 9 in FIG. This moving coil type indicator 9 is a means for controlling the positioning and switching of each of the above reference patterns to match the window 7 and the foot position.
“Using stepper motors and other drive devices”
In the case of the example shown in FIG. 8, by controlling the current value applied to the moving coil 9b, each reference pattern can be selectively applied to the window 8 by tilting the indicator needle 9a at an arbitrary angle. At this time, the reference pattern on the window 8 is imaged by the exposure optical system with respect to the photoreceptor surface, which is the image surface.
It is located on the so-called object plane.

Here, the indicator needle 9a swings around one point. Therefore,
By setting the arc centered at the center of the swing to match the curvature of the movable member 8, each reference pattern can be fixedly set according to the swing of the indicator needle 9a. This is done by changing the position of the window 7.

Referring to FIG. 3, under the illustrated state, an exposure lamp 10, which is a strong light emitting source such as a halogen lamp, is in a home position together with a first mirror 11, a second mirror 12, etc., and in this state Under this, the reflection of the mask plate 6 irradiated by the exposure lamp 10 is the first mirror 11 + the second mirror 11
7-12- + through lens 3 → third mirror 14 → fourth mirror 15 in the order of reflection, and then
6).

Around the photosensitive drum 16, several process members are arranged, similar to a well-known dry type electrophotographic apparatus. The rotary blade of the photosensitive drum 16 The rotary blade of the photosensitive drum 16 The names of the parts are listed in the same order as the following: 17 C charging charger, 18 static elimination lamp, 19 developing unit, 20 i transfer charger, 21 U separation charger. 22
is a separation claw, code 23 is a cleaning unit, code 24
(The lower charger is shown below.Static charge removal lamp 18
The portion of the surface of the photoreceptor drum between the developing unit 19 and the developing unit 19 is an exposure portion, and exposure light is irradiated to the portion p5. Also, separation claw 2
A light emitting diode 25a1 is disposed at a position where the surface of the photoreceptor drum located between the two and the IJ-ning unit 23 can be irradiated. , a phototransistor 25b for receiving reflected light at a position where it can receive the reflected light 7)r
The detectors 0 and 0 installed respectively are collectively referred to as a detector, and are designated by the reference numeral 25. The passage shown in Figure 10, detector 2
The output of 5 is A/B converted by AD comparator 26 and converted to C.
Each time the reference pattern input signal 270 is received at the core of the PU 27, arithmetic processing such as comparison with a predetermined reference value is performed, and a toner replenishment signal is output as necessary, and the motor 28 is driven by this toner replenishment signal. Then, the toner replenishing device 29 is driven, and toner is replenished.

Next, a switching control method for each reference pattern will be explained.

(1) When there is no need to judge the developing ability.

The determination of the developing ability and the toner replenishment operation, which is one of the measures therefor, do not necessarily need to be performed every copy cycle. Therefore, when these are not used, the reference patterns P2, P3, and P4 for determining the developing ability must be shielded from the strong light from the exposure lamp 10 to prevent the patterns themselves from discoloring. If the window 7 is filled with white, unnecessary development will not be performed on a portion of the photosensitive drum 16.

Therefore, in this situation, in suspension, the white standard turn Px
', position it at window 7.

(2) When determining developing ability.

When determining the developing ability, the exposure of the exposure lamp 10, the first mirror 11, the second mirror 12, etc., and the trench set at the home position shown in FIG.
The photosensitive drum 16 is rotated to execute a process similar to a normal copy cycle. However, since there must be no change in the detector 250 until the toner image corresponding to the reference pattern rotates around the detector 250, members related to transfer, sheet feeding, etc. are not made to function. The members include, for example, the upper paper feed roller 30, the lower paper feed roller 31, the separation charger 21, the separation claw 22, and the like. When detecting the density, the photosensitive drum 1 is rotated while being charged in the dark, and at the same time, the reference patterns P2, P3, and P4 are sequentially switched. Then, an image of each reference pattern is formed on the photosensitive drum 1 and exposed to light, and an electrostatic latent image is carried thereon. The toner adheres to the area corresponding to the dark part of the pattern and is visualized, passing through the area of the detector 25. At the time of this passing, each reference no turn P2 s P
The amount of reflected light from each developing section corresponding to 3s P4 is sequentially read by the circuit shown in FIG.

In addition, when exposing each of the reference patterns P2, P3, and P4, in the case of the reference pattern P2, by keeping the reference pattern P2 stationary for a certain period of time at a position that coincides with the window 7, the reference pattern P2 is made to correspond to a white pattern. Carrying an electrostatic latent image. In the case of the reference pattern P3, if the reference pattern P3 is left stationary for a certain period of time at a position that coincides with the window 7, a latent image of n lines perpendicular to the axial direction of the photoreceptor drum is formed on the photoreceptor drum. Furthermore, regarding the reference pattern P4, since exposure is performed while the photoreceptor drum is rotating, if it is kept stationary at the position corresponding to window 7, the image will be washed away. In order to prevent this, when exposing the reference pattern P4', the sequence is switched from reference pattern P5 to reference nook turn P4 to reference pattern P5 in a short period of time to prevent the image from drifting.

By the way, regarding the image development corresponding to the reference pattern P2, the average value of the amount of reflected light is detected, and the amount of toner adhering to the background of the photoreceptor is checked. Further, regarding the image development corresponding to the reference pattern P3, the lowest value of the amount of reflected light among the three black lines is detected. Furthermore, regarding the developed image corresponding to the reference pattern P4, the maximum and minimum values of the amount of reflected light for that 100 million yen are detected. Then, compare the difference in the amount of reflected light between the developed image corresponding to the reference pattern P3 and the developed image corresponding to the reference pattern &, and when the difference becomes smaller than a predetermined reference value, it is determined that the toner is exhausted. The CPU 27 outputs a toner replenishment signal to operate the toner replenishment device 29 (1), replenishes the developing unit 19 with toner, and controls the toner adhesion amount to a predetermined constant level. In this example, multiple reference patterns formed on the movable member can be exposed on the photoreceptor by switching and controlling the plurality of reference patterns formed on the movable member instead of moving the exposure optical system. Since it is sufficient that the detector 25 crosses the developing section corresponding to the reference pattern one after another, one
Also, when you are not checking the toner density, place each reference pattern for checking the developing capacity in a dark area, and use a dedicated white reference pattern (turn in the core area instead). Therefore, the problems associated with the prior art mentioned at the beginning are solved.

In addition, especially in the case of each reference pattern as described in the above example,
It has the advantage of being able to detect developer fatigue at an early stage.

This point will be explained below.

In other words, in the conventional toner 11 degree control device, the response to so-called solid images is good, but the response to so-called line images (characters, line segments, etc.) is poor, and the response to so-called line images is poor. Even when the density decreases, toner is not properly replenished, and the user is left with low-density line images and images of poor quality.

In general, there is a visible image due to new developer and a visible image due to tired developer, as well as a solid image and a line image! !
Figure 6 shows the development characteristics of a standard pattern that becomes a solid image due to changes in developer over time.Curve 100 shows the development characteristics with new developer, and curve 200 shows the development characteristics of a standard pattern with a new developer. The arrow indicates the approximately central part (other than the edge part) of the pattern control system that shows the development characteristics of exhausted developer and uses only a solid image as a reference pattern for utilizing the developing capacity. 300
The toner density is controlled by detecting the image density at the level indicated by . As can be seen from FIG. 6, as the developer becomes fatigued, the image density level indicated by arrow 300 tends to increase slightly because the toner is no longer distributed as directed by the edge effect.

Further, FIG. 7 shows the development characteristics of line images due to changes in developer over time, where curve 400 shows the development characteristics of new developer and curve 500 shows the development characteristics of tired developer. Line images are inherently susceptible to the effects of developer fatigue, and image density decreases momentarily due to developer fatigue. In addition, in the solid pattern control method, as is clear from FIG. constant f
Since the toner density is controlled, line images suffer from even more reduction in image viscosity, which causes the above-mentioned problem in response to line images.

However, in the present invention, a plurality of reference patterns can be set, and each reference pattern can include one corresponding to a solid image (reference pattern P4) and one corresponding to a line image (reference pattern P+). , each developing power corresponding to both patterns) can be provided for determining the developing ability, and the responsiveness to line images can be improved.

In the above, the maximum value and minimum value of the image corresponding to the reference pattern P4 were detected because the difference between the two was understood as the difference in edge effect in Fig. 6, and the difference between the two was compared and the difference was found to be small. This is to judge the fatigue of the developer when it becomes ◎ Similarly, in the above, the minimum value of the amount of reflected light in each black line of the developed image corresponding to the reference pattern P3 was determined as follows.
It can be said that this was a method for determining the degree of fatigue of the developer appearing in the line image under the worst conditions.In addition, other methods for determining developer fatigue can be made by detecting the amount of reflected light from the developed image of the reference pattern P4. As a method, the difference between the lowest value and the average value of the amount of reflected light can also be used as a guideline for determination based on the fact that the difference decreases as the developer becomes fatigued, based on experimental data.

Alternatively, as a simple method of determination, the average value of the amount of light reflected from the image plane may be detected. This is because as the developer becomes fatigued, there is a tendency for the overall developed image density to gradually increase, and this characteristic is utilized. In this case, it is determined that the developer is exhausted when the average density exceeds a certain value.

Roughly speaking, as another determination method, the minimum value of the amount of reflected light during development corresponding to the reference pattern P4C and the reference pattern P
It can also be determined that the developer is exhausted when the difference from the minimum value of the reflected light amount of each black line of the developed image corresponding to No. 3 falls below a certain value.

As described above, various determination methods can be considered, and n; b may be appropriately selected and used depending on the characteristics of the developer.

Regarding the measurement of the amount of reflected light from the developer with respect to the reference pattern P2, as the developer becomes fatigued, the amount of charge per mass tends to decrease. There is a phenomenon in which toner tends to adhere even if the latent image potential on the surface of the photoreceptor is the same.Fatigue is determined by understanding this situation.

Next, effects other than those intended by the present invention will be described.

Conventionally, when attempting to provide multiple reference patterns, the area of the reference patterns is limited because the attachment points are at the edges of the contact glass. However, in the present invention, since the reference pattern is formed on a movable member separate from the contact glass, the area of the pattern must be made small. Since a reference pattern can be obtained, various test modes are possible.

Finally, in FIG. 3, reference numeral 34 used in the above description indicates the main motor, reference numeral 35 indicates the paper ejection roller, and reference numeral 36 indicates the copy tray.

[Brief explanation of drawings]

1 and 2 respectively explain the relationship between the array state of reference patterns and the scanning direction in the prior art, and FIG. 5 is a block diagram of a dry electrophotographic apparatus to which the present invention is applied.
Figure 5 is a side view of the toner concentration 11 control device according to the present invention.
The figure is a plan view of the edge of a contact glass that is an embodiment of the present invention, Figure 6 is a diagram explaining the fatigue characteristics of the developer in a solid image, and Figure 7 is a diagram explaining the fatigue characteristics of the developer in a line image. 8 is a perspective view of a toner concentration control device according to an embodiment of the present invention, FIG. 9 is an explanatory diagram of a movable member and a reference pattern, and FIG. 10 is a detection diagram in the toner concentration control device according to the present invention. FIG. 3 is a circuit diagram of a functional part that processes data. 7... Window, 8... Movable member, 9... Moving coil type indicator 〇

Claims (1)

[Claims] 1. Detecting the image density of an image pattern for density detection, which is visualized as a pattern corresponding to a reference pattern for determining developing ability, and comparing this n with a certain reference value. , when it is determined that the value is below the standard value (by taking measures such as replenishing toner appropriately, the 7! time of the image that is visualized corresponding to the original image is maintained at a certain level). A toner density control device for an electrophotographic copying machine, etc., includes a movable member having a plurality of reference patterns, and a means for controlling the movement of the movable member, wherein a movable member having a plurality of reference patterns is selected from among the plurality of reference patterns in the movable member. A toner concentration control device comprising a switching means for positioning a reference pattern at a predetermined spatial position on an object plane of an exposure optical system via a window. 2. The standard according to claim 1. A toner density control device characterized in that the patterns include a white pattern other than a reference pattern for determining developing ability. 3. The reference pattern described in claim 1 includes three white patterns and a line. A toner density control device characterized by a pattern and a black pattern. 4. The switching means according to claim 1 uses a moving coil type or moving iron piece type indicator. Characteristic toner density control device.